Magnetoresistive element, magnetic head and magnetic recording/reproducing apparatus

ABSTRACT

A magnetoresistive element has a first magnetic layer and a second magnetic layer separate from each other, the first magnetic layer and the second magnetic layer each having a magnetization whose direction is substantially pinned, and a non-magnetic conductive layer formed in contact with the first magnetic layer and the second magnetic layer and electrically connecting the first and second magnetic layers, the non-magnetic conductive layer forming a path of spin-polarized electrons from one of the magnetic layer to the other magnetic layer, the non-magnetic conductive layer comprising a portion located between the first magnetic layer and the second magnetic layer, the portion being a sensing area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 10/895,844,filed Jul. 22, 2004, which is based upon and claims the benefit ofpriority from prior Japanese Patent Application No. 2003-201131, filedJul. 24, 2003, the entire contents of both of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistive element, magnetichead and magnetic recording/reproducing apparatus.

2. Description of the Related Art

By virtue of the discovery of a magnetoresistive element that exhibits agiant magnetoresistive effect (GMR), the performance of magneticdevices, in particular, magnetic heads, has been significantly enhanced.In particular, since a spin-valve (SV) film has a structure that can beeasily applied to magnetic devices, it has enormously contributed totechnical development of magnetic discs.

A spin-valve film comprises two ferromagnetic layers and a non-magneticlayer interposed therebetween. One of the ferromagnetic layers, called apinned layer, has a magnetization whose direction is pinned by, forexample, an antiferromagnetic layer, while the other ferromagneticlayer, called a free layer, has a magnetization whose direction is madeto respond to an external magnetic field. In this structure, a giantmagnetoresistance change can be obtained in accordance with a change inthe relative angle made by magnetization directions of the pinned andfree layers. Theoretically, the spin-valve film enables efficientmagnetic field detection if the magnetization direction of the freelayer is made parallel to the track width direction when the externalmagnetic field is zero, and if the magnetoresistance change is generatedwhen the magnetization direction of the free layer is changed inaccordance with the external magnetic field (see U.S. Pat. No.5,206,590).

Conventional spin-valve films are mainly of a current-in-plane (CIP)type in which a sense current is made to flow parallel to the filmplane. On the other hand, spin-valve films of acurrent-perpendicular-to-plane (CPP) type are now being developed, inwhich a sense current is made to flow substantially perpendicular to thefilm plane, because they exhibit a much greater GMR effect than the CIPtype. At the present stage, CPP spin-valve films are expected as amost-promising technique for realizing a magnetic recording/reproducingapparatus having an areal recording density of 200 Gbit/inch² (Gbpsi) ormore.

To achieve a high recording density, the size of the spin-valve filmmust inevitably be reduced. In other words, it is necessary to narrowthe track width recorded on a medium for high recording density.Accordingly, it is also necessary to reduce the size of the free layer,as a sensing layer, of a spin-valve film. For instance, the track widthof a spin-valve film is as narrow as about 100 nm if the areal recordingdensity is 200 Gbit/inch², about 50 nm for an areal recording density of500 Gbit/inch², and about 35 nm for an areal recording density of 1Tbit/inch². If the conventional CPP spin-valve film size is reduced inaccordance with an areal recording density of 500 Gbit/inch² or more,the following two serious problems may occur.

Firstly, a vortex domain may occur in the free layer. Assuming that thesame sense current as in the conventional case is made to flow in theperpendicular direction, the smaller the free layer size, the higher thecurrent density in the free layer. This causes a vortex domain in thefree layer due to a current magnetic field. When a vortex domain occursin the free layer, the magnetization direction of the free layer cannotbe made parallel to the track width direction, resulting inunsatisfactory magnetic field detection. Such a vortex domain occurswhen the current density is about 10⁸ A/cm² or more. If, for example,the recording density is S00 Gbit/inch² and the sense current is 3 mA,the current density is 1.2×10⁸ A/cm² and accordingly a vortex domainoccurs. In this case, it is not an effective countermeasure to reducethe sense current to about 1 mA so as to avoid the occurrence of thevortex domain. This is because the countermeasure involves reduction inthe signal output voltage (i.e., current×resistance change).

Secondly, the influence of a spin transfer torque phenomenon may beserious (see, for example, Journal of Magnetism and Magnetic Materials159 (1996), L1-L7). Assume that the size (one side) of an element havingtwo magnetic layers and a non-magnetic layer interposed therebetween isset to 100 nm or less, and a current with a current density of 10⁷ to10⁸ A/cm² is made to flow through the element in the perpendiculardirection. In this case, a phenomenon is observed in which a spin torqueof one magnetic layer is transferred to the other magnetic layer,thereby changing the magnetization direction of the other magneticlayer. The occurrence of such a spin transfer torque phenomenon in theCPP spin-valve film means that, even if the external magnetic field froma medium is zero, the sense current changes the magnetization directionof the free layer. In other words, the phenomenon makes it difficult torealize the operating principle of the spin valve that the magnetizationdirection of the free layer is changed by the medium magnetic field tothereby detect a magnetoresistance change. In a CPP spin-valve filmcorresponding to a recording density of 500 Gbit/inch² or more, theelement size and current density are significantly influenced by thespin transfer torque phenomenon. Therefore, the operation of the CPPspin-valve film is inhibited by the phenomenon.

As stated above, in a CPP spin-valve structure of a small element size,two problems, i.e., the vortex domain problem and spin transfer torqueproblem, may well occur, which makes it difficult to realize a magneticrecording/reproducing apparatus having a recording density of 500Gbit/inch² or more.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide a novel magnetoresistiveelement for high-density recording of 500 Gbit/inch² or more, a magnetichead using the magnetoresistive element, and a magneticrecording/reproducing apparatus equipped with the magnetic head.

According to an aspect of the invention, there is provided amagnetoresistive element comprising: a first magnetic layer and a secondmagnetic layer separate from each other, the first magnetic layer andthe second magnetic layer each having a magnetization whose direction issubstantially pinned; and a non-magnetic conductive layer formed incontact with the first magnetic layer and the second magnetic layer andelectrically connecting the first and second magnetic layers, thenon-magnetic conductive layer forming a path of spin-polarized electronsfrom one of the magnetic layer to the other magnetic layer, thenon-magnetic conductive layer comprising a portion located between thefirst magnetic layer and the second magnetic layer, the portion being asensing area.

In the above magnetoresistive element, the sensing area of thenon-magnetic conductive layer located between the first magnetic layerand the second magnetic layer has a length of 100 nm or less.

According to another aspect of the invention, there is provided amagnetic head comprising the above magnetoresistive element.

According to yet another aspect of the invention, there is provided amagnetic recording/reproducing apparatus comprising a magnetic recordingmedium and the above magnetic head.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view of a magnetoresistive element according to anembodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 2 is a sectional view of a magnetoresistive element according to anembodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 3 is a view for explaining the positional relationship between themagnetoresistive element according to an embodiment of the invention anda track on the magnetic disc, the magnetoresistive element is shown by asectional view;

FIG. 4 is a sectional view illustrating the magnetoresistive elementaccording to an embodiment of the invention and a magnetic discsectioned along a plane vertical to a surface of the magnetic disc;

FIG. 5 is a graph illustrating the dependency of the MR ratio of themagnetoresistive element according to an embodiment of the inventionupon the thickness t of the non-magnetic conductive layer of theelement;

FIG. 6 is a graph illustrating the dependency of the MR ratio of themagnetoresistive element according to an embodiment of the inventionupon the width h of the non-magnetic conductive layer of the element,the thickness t of the non-magnetic conductive layer being set to 1 nm;

FIG. 7 is a graph illustrating the dependency of the MR ratio of themagnetoresistive element according to an embodiment of the inventionupon the width h of the non-magnetic conductive layer of the element,the thickness t of the non-magnetic conductive layer being set to 5 nm;

FIG. 8 is a sectional view of a magnetoresistive element according toanother embodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 9 is a sectional view of a magnetoresistive element according toyet another embodiment of the invention, taken along a plane parallel tothe air-bearing surface of the magnetoresistive element;

FIG. 10 is a sectional view of a magnetoresistive element according to afurther embodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 11 is a sectional view of a magnetoresistive element according to ayet further embodiment of the invention, taken along a plane parallel tothe air-bearing surface of the magnetoresistive element;

FIG. 12 is a sectional view of a magnetoresistive element according toanother embodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 13 is a sectional view of a magnetoresistive element according toanother embodiment of the invention, taken along a plane parallel to theair-bearing surface of the magnetoresistive element;

FIG. 14 is a view for explaining the positional relationship between themagnetoresistive element of FIG. 13 and a track on the magnetic disc;

FIG. 15 is a sectional view illustrating the magnetoresistive element ofFIG. 13 and a magnetic disc sectioned along a plane vertical to asurface of the magnetic disc;

FIG. 16 is a sectional view illustrating a magnetoresistive elementaccording to a further embodiment and a magnetic disc sectioned along aplane vertical to a surface of the magnetic disc;

FIG. 17 is a view for explaining the positional relationship between themagnetoresistive element of FIG. 16 and a track on the magnetic disc,the magnetoresistive element is shown by its sectional view parallel toa surface of the magnetic disc;

FIG. 18 is a perspective view illustrating a magnetic head assemblyaccording to an embodiment of the invention; and

FIG. 19 is a perspective view of a magnetic recording/reproducingapparatus according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In consideration of the fact that the problems of conventionalspin-valve films are raised due to their soft-magnetic free layer, theinventors have studied a magnetoresistive element that can realize adesired function without a free layer. As long as employing magneticlayers whose magnetization directions are not substantially changed, theproblems due to a vortex domain and spin transfer torque can be avoided.The inventors have paid attention to the fact that the dimensions of amagnetoresistive element corresponding to a high recording density of500 Gbit/inch² or more are in physical areas at which a quantum effectcan occur. Further, they have studied that a non-magnetic conductivelayer in which conduction electrons for sensing an external magneticfield can be used as a sensing area. It is expected that conductionelectrons flowing through the non-magnetic conductive layer can sensechanges in an external magnetic field with much higher sensitivity thanconduction electrons flowing through a magnetic layer. This is becausethe spin information obtained from conduction electrons flowing in themagnetic layer is influenced by the magnetization direction of themagnetic layer itself to a much higher degree than the influence of anexternal magnetic field upon the conduction electrons. In other words, achange in external magnetic field can hardly be detected from theconduction electrons in the magnetic layer.

The element that uses a non-magnetic conductive layer as a sensing areamust satisfy following structural requirements:

Firstly, conduction electrons must have up- or down-spin informationsince if they have no spin information, they cannot sense a change inexternal magnetic field.

Secondly, a non-magnetic conductive layer used as a sensing area must bein contact with a magnetic layer. This is for the following reason: Ingeneral, conduction electrons flowing through a non-magnetic layer havetheir spin information averaged, not biased to up- or down-spininformation. Therefore, it is needed to inject, into the non-magneticconductive layer, conduction electrons with up- or down-spininformation. To this end, it is necessary to make the non-magneticconductive layer contact a magnetic layer that contains conductionelectrons having a larger number of up-spins than down-spins (or viceversa) (i.e., conduction electrons having spin information).

Thirdly, the non-magnetic conductive layer must contact a magnetic layer(second magnetic layer) other than the above-mentioned magnetic layer(first magnetic layer). This is because even if the spin information ofconduction electrons in the non-magnetic layer (sensing area) is changedby an external magnetic field, the resistance change does not easilyoccur, therefore it is needed to re-inject conduction electrons havingcertain spin information into the magnetic layer having spininformation. When the conduction electrons with spin information arere-injected from the non-magnetic conductive layer to the secondmagnetic layer, the resistance changes depending upon whether the spininformation is up or down, thereby generating a magnetoresistanceeffect.

In short, a magnetoresistive element according to the embodiments of thepresent invention comprises a first magnetic layer and a second magneticlayer separate from each other, the first magnetic layer and the secondmagnetic layer each having a magnetization whose direction issubstantially pinned, and a non-magnetic conductive layer formed incontact with the first magnetic layer and the second magnetic layer andelectrically connecting the first and second magnetic layers, thenon-magnetic conductive layer forming a path of spin-polarized electronsfrom one of the magnetic layer to the other magnetic layer, thenon-magnetic conductive layer comprising a portion located between thefirst magnetic layer and the second magnetic layer, the portion being asensing area.

Referring to FIGS. 1 to 4, a description will be given of amagnetoresistive element, according to an embodiment of the invention,used for a read head reading data recorded on a magnetic recordingmedium. FIGS. 1 and 2 are sectional views of the magnetoresistiveelement, taken along a plane parallel to the air-bearing surface (ABS)of the magnetoresistive element. FIG. 3 is a view for explaining thepositional relationship between the magnetoresistive element shown inFIGS. 1 and 2 and a track on the magnetic recording medium (magneticdisc). FIG. 4 is a sectional view illustrating the magnetoresistiveelement of the embodiment and a magnetic disc sectioned along a verticalplane.

As seen from FIGS. 1 and 2, an underlayer 2 of Al₂O₃ is formed on asubstrate 1, and a non-magnetic conductive layer 3 of Cu having athickness of 0.5 to 5 nm is formed on the underlayer 2. First and secondmagnetic layers 11 and 12 made of, for example, Co₉₀Fe₁₀ are formed onthe non-magnetic layer 3 such that the layers 11 and 12 are separatefrom each other but both are in contact with the layer 3. Themagnetization direction of the first and second magnetic layers 11 and12 is substantially pinned. In this embodiment, the magnetizationdirection of the layers 11 and 12 is pinned upward from the ABS. Thenon-magnetic conductive layer 3 serves as a path for permittingspin-polarized electrons to flow from the first magnetic layer 11 to thesecond magnetic layer 12. Electrodes 21 and 22 are provided on the firstand second magnetic layers 11 and 12, respectively.

The underlayer 2 may be formed of a material other than Al₂O₃. Forexample, another oxide, such as SiO₂, may be used as an insulationmaterial. Further, a buffer layer or orientation seed layer may beprovided between the underlayer 2 and non-magnetic conductive layer 3.For example, the seed layer may be formed of an alloy, oxide or nitridecontaining Ta, Ti, Cr, V, Zr, Nb, Mo or W. The seed layer may also beformed of a metal having a fcc or hcp structure.

As shown in FIGS. 3 and 4, the portion of the non-magnetic conductivelayer 3 located between the first and second magnetic layers 11 and 12is defined as a sensing area sensing an external magnetic field, and ispositioned above a track (having a width TW) on a magnetic disc 101. Thelength of the sensing area is determined in accordance with the trackwidth. Specifically, the length of the sensing area is set to 100 nm orless, and preferably to 10 to 100 nm. In FIGS. 3 and 4, t represents thethickness of the non-magnetic conductive layer 3, and h represents thewidth of the layer 3 that is perpendicular to the length of the sensingarea. The width h of the non-magnetic conductive layer 3 is set to about10 to 300 nm, preferably to 100 nm or less. It should be noted thatdimensions of regions other than the sensing area are not particularlyrestricted as shown in FIGS. 3 and 4.

Referring to FIGS. 1 and 2, the operation of the magnetoresistiveelement of the embodiment will be described. FIG. 1 shows a case whereexternal magnetic field information is “0” (upward), while FIG. 2 showsa case where it is “1” (downward).

A sense current is made to flow from the electrode 21 to thenon-magnetic conductive layer 3 via the first magnetic layer 11. As aresult, spin-polarized conduction electrons are injected from the firstmagnetic layer 11 into the non-magnetic conductive layer 3. Conductionelectrons sense an external magnetic field while passing through thesensing area of the non-magnetic conductive layer 3.

In the case of FIG. 1, the external magnetic field information is “0”,which indicates that the magnetization direction of the externalmagnetic field is the same as that of the first magnetic layer 11.Therefore, conduction electrons are not subjected to a change in spininformation while passing through the sensing area of the non-magneticconductive layer 3. Further, since the magnetization direction of thesecond magnetic layer is identical to that of the first magnetic layer11, conduction electrons are injected from the non-magnetic conductivelayer 3 into the second magnetic layer 12 with the spin information ofthe conduction electrons unchanged. In other words, there is no changein the spin information, and therefore the resistance of themagnetoresistive element is low. Thus, the external magnetic fieldinformation “0” is detected as a state in a low resistance.

In the case of FIG. 2, the external magnetic field information is “1”,which indicates that the magnetization direction of the externalmagnetic field is opposite to that of the first magnetic layer 11.Therefore, the spin direction of conduction electrons is changed by theexternal magnetic field while the electrons are passing through thesensing area of the non-magnetic conductive layer 3. In an extreme case,the spin direction is completely reversed by the external magneticfield. That is, the spin direction of the conduction electrons injectedfrom the non-magnetic conductive layer 3 is completely opposite to thatof the conduction electrons contained in the second magnetic layer 12.In this state, when conduction electrons are injected from thenon-magnetic conductive layer 3 into the second magnetic layer 12, theirspin direction must be reversed at the interface of the layers 3 and 12,which increases the resistance. Thus, the external magnetic fieldinformation “1” is detected as a state in a high resistance.

As described above with reference to FIGS. 1 and 2, although themagnetization direction of the first and second magnetic layers 11 and12 is not changed substantially by the external magnetic field, theresistance of the magnetoresistive element is changed between alow-resistance state and high-resistance state, depending upon theexternal magnetic field. This is the feature, concerning the operationprinciple, of the magnetoresistive element of the embodiment, whichessentially differs from the conventional spin-valve film. Morespecifically, the magnetoresistive element of the embodiment has, asmagnetic layers, only the first and second magnetic layers 11 and 12whose magnetization direction is firmly pinned so that it is not changedsubstantially by an external magnetic field, and does not have a sensingmagnetic layer (free layer) whose magnetization direction is changed bythe external magnetic field. Accordingly, the magnetoresistive elementof the invention is advantageously free from the aforementioned problemsof the prior art, i.e., the occurrence of a vortex domain in the freelayer and the influence of the spin transfer torque phenomenon.

As described above, the magnetoresistive element according to theembodiments of the present invention can detect a magnetoresistanceeffect using the simple structure shown in FIGS. 1 to 4. This elementcannot easily be inferred from the conventional spin-valve film.

A description will now be given of the dimensions of themagnetoresistive element according to the embodiments of the presentinvention. To provide the advantage of the magnetoresistive element ofthe embodiment, the thickness t of the non-magnetic conductive layer 3shown in FIG. 3 and the width h of the layer 3 shown in FIG. 4 areregarded as important dimensions.

FIG. 5 illustrates the dependency of the MR ratio of themagnetoresistive element upon the thickness t of the non-magneticconductive layer 3. The MR ratios shown in the figure were measuredusing magnetoresistive elements in which the non-magnetic conductivelayer 3 is formed of Cu, and the width h of the layer 3 is set to 80 nm.As shown in FIG. 5, no effective MR ratio can be obtained if thethickness t-of the non-magnetic conductive layer 3 is more than 5 nm.From this, it is understood that the thickness t of the non-magneticconductive layer 3 serving as a sensing area is an important parameter.It is preferable that the thickness t of the layer 3 be smaller than themean free path for the layer 3.

FIG. 6 illustrates the dependency of the MR ratio upon the width h ofthe non-magnetic conductive layer 3, the thickness t of the layer 3being set to 1 nm. It is understood from FIG. 6 that when the thicknesst of the layer 3 is set to a value (in this case, 1 nm) that enables asufficient magnetoresistance effect to be generated, a rather highmagnetoresistance effect can be obtained even if the width h (elementwidth) of the layer 3 is broadened up to about 300 nm.

FIG. 7 illustrates the dependency of the MR ratio upon the width h ofthe non-magnetic conductive layer 3, the thickness t of the layer 3being set to 5 nm. It is understood from FIG. 7 that even if thethickness t of the non-magnetic conductive layer 3 is as thick as 5 nm,an effective MR ratio can be obtained by reducing the width h of thelayer 3 less than 80 nm.

The materials used for the magnetoresistive element according to theembodiments of the present invention will be described.

The material for the non-magnetic conductive layer includes Cu, Au, Ag,Ru, Rh and Al.

The material for the first and second magnetic layers 11 and 12 includesCo, Fe or Ni, or an alloy containing at least one of these elements,such as CoFe alloy, FeCo alloy, CoNi alloy or NiFe alloy, typically,Co₉₀Fe₁₀. It is preferable that the first and second magnetic layers 11and 12 have a thickness of about 2 to 20 nm. If the first and secondmagnetic layers 11 and 12 are too thin, their function as a source forspin-polarized electrons to be injected is degraded, and therefore thelower limit of the film thickness is about 2 nm.

Since those magnetic layers serve as a source for injectingspin-polarized electrons into the non-magnetic conductive layer, it ispreferable that the polarization rate for up-electrons anddown-electrons be high. Therefore, it is optimal to use a material,called a half metal, in which only up-electrons or down-electrons exist.The half metal includes Fe₃O₄, Cr₂O₃, a perovskite oxide such asLaSrMnO, and a Heusler alloy such as NiMnSb and CoMnGe.

Further, since spin injection is performed through the interfaces of thefirst and second magnetic layers 11 and 12 and the non-magneticconductive layer 3, it is preferable that the materials of the layers11, 12 and 3 be a combination that enables sharp interfaces to be easilyformed. Specifically, it is preferable that the first and secondmagnetic layers 11 and 12 be immiscible with the non-magnetic conductivelayer 3. For instance, if the magnetic layers contain Co as a mainelement, it is preferable that the non-magnetic conductive layer beformed of Cu, Au, etc. If the magnetic layers contain Ni as a mainelement, it is preferable that the non-magnetic conductive layer beformed of Ru, Ag, etc.

In order to pin the magnetization direction of the first and secondmagnetic layers 11 and 12, antiferromagnetic layers, for example, may beprovided in contact with the magnetic layers, respectively. Theantiferromagnetic layer includes Mn-based anti-ferromagnetic layer ofPtMn, IrMn, etc. The thickness of the antiferromagnetic layers is set toabout 10 to 20 nm.

In the magnetoresistive element shown in FIG. 8, antiferromagneticlayers 31 and 32 are interposed between the first and second magneticlayers 11 and 12 and the electrodes 21 and 22, respectively. Except forthe antiferromagnetic layers, this element has the same structure asthat shown in FIGS. 1 and 2.

The magnetization direction of the first and second magnetic layers 11and 12 may be pinned by a so-called synthetic AF structure (magneticlayer/Ru layer/magnetic layer/antiferromagnetic layer) as shown in FIG.9. In the magnetoresistive element shown in FIG. 9, the first magneticlayer 11 has a stacked structure of a magnetic layer 11 a, Ru layer 11 band magnetic layer 11 a. Similarly, the second magnetic layer 12 has astacked structure of a magnetic layer 12 a, Ru layer 12 b and magneticlayer 12 a. Further, antiferromagnetic layers 31 and 32 are interposedbetween the first and second magnetic layers 11 and 12 and electrodes 21and 22, respectively. Except for these structures, the element of FIG. 9has the same structure as that shown in FIGS. 1 and 2.

The first and second magnetic layers 11 and 12 may be formed of hardmagnetic layers in order to pin the magnetization directions. In thiscase, the hard magnetic layers can be formed of a CoPt alloy, CoCralloy, FePt alloy, etc.

The electrodes 21 and 22 can be formed of Cu, Au, Al, etc.

To form thin films used in the magnetoresistive element according to theembodiments of the present invention, various methods such assputtering, MBE, ion-beam sputtering, and CVD can be utilized. Thesedeposition methods can control the thickness of such a thin film as thenon-magnetic conductive layer. Further, to define film dimensions otherthan the film thickness, patterning by lithography may be performed.Specifically, a stepper or electron-beam lithography equipment can beused to define, for example, the width h of the non-magnetic conductivelayer, or the length of a sensing area corresponding to the track width.

Magnetoresistive elements according to another embodiments of theinvention will now be described.

The magnetoresistive element shown in FIG. 10 differs from that of FIGS.1 to 4 in that the magnetization direction of the magnetic layer 11 isopposite to that of the magnetic layer 12. In the element of FIG. 10,when an external (recording medium) magnetic field of a directionopposite to that of FIGS. 1 to 4 is applied thereto, a high resistancestate and low resistance state are obtained, respectively.

It is not always necessary to pin the magnetization direction of thefirst and second magnetic layers 11 and 12 perpendicular to the ABS. Forinstance, in the magnetoresistive element shown in FIG. 11, themagnetizations of the first and second magnetic layers 11 and 12 arepinned parallel to the ABS and in the same direction. On the other hand,in the magnetoresistive element shown in FIG. 12, the magnetizations ofthe first and second magnetic layers 11 and 12 are pinned parallel tothe ABS but in opposite directions. The magnetoresistive elements shownin FIGS. 11 and 12 operate on the same principle as mentioned above.

In a magnetoresistive element according to yet another embodiments ofthe invention, the order of stacking of thin films on the substrate maybe opposite to that in the magnetoresistive element shown in FIGS. 1 to4. That is, the electrodes may be provided close to the substrate, andthe non-magnetic conductive layer may be provided remote from thesubstrate. This magnetoresistive element will be described withreference to FIGS. 13 to 15. FIG. 13 is a sectional view of themagnetoresistive element, taken along a plane parallel to the ABS of themagnetoresistive element. FIG. 14 is a view for explaining thepositional relationship between the magnetoresistive element of FIG. 13and a track on the magnetic disc. FIG. 15 is a sectional viewillustrating the magnetoresistive element of FIG. 13 and a magnetic discsectioned along a vertical plane.

In FIGS. 13 to 15, electrodes 21 and 22 are provided on the substrate 1and separate from each other. An insulating layer 15 is arranged betweenthe electrodes 21 and 22. First and second magnetic layers 11 and 12 areprovided, separate from each other, on the electrodes 21 and 22,respectively. The insulating layer 15 is also arranged between the firstand second magnetic layers 11 and 12. Insulating layers 16 are arrangedon the side wall of the first magnetic layer 11 and that of the secondmagnetic layer 12, respectively. The magnetization direction of thefirst and second magnetic layers 11 and 12 is substantially pinned. Anon-magnetic conductive layer 3 is provided on the first and secondmagnetic layers. The non-magnetic conductive layer 3 is a path forpermitting spin-polarized electrons to flow from the first magneticlayer 11 to the second magnetic layer 12. The portion of thenon-magnetic conductive layer 3 located between the first and secondmagnetic layers 11 and 12 is defined as a sensing area sensing anexternal magnetic field, and is positioned above a track (having a widthTW) on the magnetic disc 101.

The magnetoresistive element, in which the electrodes are located closeto the substrate, and the non-magnetic conductive layer is locatedremote from the substrate, can be configured as shown in FIGS. 16 and17, such that the element is rotated by 90 degrees around an imaginaryaxis parallel to the surface of the magnetic disc 101 from theconfiguration shown in FIGS. 14 and 15. More specifically, in FIGS. 14and 15, the stacking direction of the thin films on the substrate isparallel to the ABS, whereas in FIGS. 16 and 17, it is perpendicular tothe ABS. In the latter case, however, the non-magnetic conductive layer3 on the outer surface side can be made to oppose the magnetic disc 101.

A magnetic head and magnetic recording reproducing apparatus accordingto an embodiment of the invention will be described.

FIG. 18 is a perspective view as viewed from a disc side, illustrating amagnetic head assembly, according to an embodiment of the invention,equipped with the above-described magnetoresistive element. The magnetichead assembly 50 has an actuator arm 51 with a bobbin section that holdsa driving coil. A suspension 52 is coupled to the distal end of theactuator arm 51. A head slider 53 provided with a magnetoresistiveelement according to an embodiment of the invention is attached to thedistal end of the suspension 52. Lead wires 61 for reading and writingdata is provided on the suspension 52. The lead wires 61 areelectrically connected to electrodes of the magnetic head mounted on thehead slider 53. Further, the lead wires 61 are connected to theelectrode pads 62 of the magnetic head assembly 50.

FIG. 19 is a perspective view of a magnetic recording/reproducingapparatus 100 according to an embodiment of the invention. The magneticrecording/reproducing apparatus 100 uses a rotary actuary. A magneticdisc 101 is mounted on a spindle 102, and is rotated by a motor (notshown) responsive to control signals output from a drive controller (notshown). A plurality of magnetic discs 101 may be incorporated in theapparatus 100. The actuator arm 51 of the magnetic head assembly 50shown in FIG. 18 is rotatably supported by ball bearings (not shown)provided on an upper portion and lower portion of a pivot 104 locatednear the magnetic disc 101. As shown in FIG. 18, the suspension 52 isconnected to the distal end of the actuator arm 51, and the head slider53 is attached to the distal end of the suspension 52. A voice coilmotor 105, a type of a linear motor, is provided to the proximal end ofthe actuator arm 51. The voice coil motor 105 comprises a driving coil(not shown) wound by the bobbin section of the actuator arm 51, and amagnetic circuit formed of a permanent magnet and yoke that oppose eachother with the coil interposed therebetween. The voice coil motor 105 isused to rotate the actuator arm 51. When the magnetic disc 101 isrotated, the ABS of the slider 53 floats above the surface of themagnetic disc 101 by a predetermined amount, thereby recording andreproducing data on and from the magnetic disc 101.

The above-described magnetic head and magnetic recording/reproducingapparatus can perform recording and reproduction of a high density of500 Gbit/inch² or more.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A magnetoresistive element comprising: a first magnetic layer and asecond magnetic layer separate from each other, the first magnetic layerand the second magnetic layer each having a magnetization whosedirection is substantially pinned; and a non-magnetic conductive layerelectrically connecting the first and second magnetic layers, thenon-magnetic conductive layer forming a path of spin-polarized electronsfrom the first magnetic layer to the second magnetic layer, and thenonmagnetic conductive layer comprising a portion located between thefirst magnetic layer and the second magnetic layer, the portion being asensing area, wherein the non-magnetic conductive layer is formed on aninsulating layer so as to be in contact with the first magnetic layerand second magnetic layer, the sensing area of the non-magneticconductive layer located between the first magnetic layer and the secondmagnetic layer has a length of 100 nm or less, and the magnetoresistiveelement has no magnetic layer in contact with the sensing area of thenon-magnetic conductive layer.
 2. The magnetoresistive element accordingto claim 1, wherein the non-magnetic conductive layer has a thickness of0.5 nm to 5 nm.
 3. The magnetoresistive element according to claim 1,wherein the non-magnetic conductive layer has a width of 100 nm or less,the width being perpendicular to the length of the sensing area of thenon-magnetic conductive layer.
 4. The magnetoresistive element accordingto claim 1, wherein the non-magnetic conductive layer contains at leastone element selected from the group consisting of Cu, Au, Ag, Ru, Al andRh.
 5. The magnetoresistive element according to claim 1, wherein thefirst magnetic layer and the second magnetic layer contain at least oneelement selected from the group consisting of Co, Fe and Ni.
 6. Themagnetoresistive element according to claim 1, further comprisingantiferromagnetic layers provided in contact with the first magneticlayer and the second magnetic layer, respectively.
 7. Themagnetoresistive element according to claim 1, wherein the firstmagnetic layer and the second magnetic layer are formed of a hardmagnetic layer containing Co or Fe.
 8. The magnetoresistive elementaccording to claim 1, wherein the first magnetic layer and the secondmagnetic layer are disposed on the same surface of the non-magneticconductive layer with a distance which defines a track width of themagnetoresistive element.
 9. A magnetoresistive element comprising: afirst magnetic layer and a second magnetic layer separate from eachother, the first magnetic layer and the second magnetic layer eachhaving a magnetization whose direction is substantially pinned; and anon-magnetic conductive layer electrically connecting the first andsecond magnetic layers, the non-magnetic conductive layer forming a pathof spin-polarized electrons from the first magnetic layer to the secondmagnetic layer, and the nonmagnetic conductive layer comprising aportion located between the first magnetic layer and the second magneticlayer, the portion being a sensing area, wherein the non-magneticconductive layer is formed on an insulating layer so as to be in contactwith the first magnetic layer and second magnetic layer, the sensingarea of the non-magnetic conductive layer located between the firstmagnetic layer and the second magnetic layer has a length of 100 nm orless, and the magnetization of the first and second magnetic layers ispinned upward from an air-bearing surface.
 10. The magnetoresistiveelement according to claim 9, wherein the non-magnetic conductive layerhas a thickness of 0.5 nm to 5 nm.
 11. The magnetoresistive elementaccording to claim 9, wherein the non-magnetic conductive layer has awidth of 100 nm or less, the width being perpendicular to the length ofthe sensing area of the non-magnetic conductive layer.
 12. Themagnetoresistive element according to claim 9, wherein the non-magneticconductive layer contains at least one element selected from the groupconsisting of Cu, Au, Ag, Ru, Al and Rh.
 13. The magnetoresistiveelement according to claim 9, wherein the first magnetic layer and thesecond magnetic layer contain at least one element selected from thegroup consisting of Co, Fe and Ni.
 14. The magnetoresistive elementaccording to claim 9, further comprising antiferromagnetic layersprovided in contact with the first magnetic layer and the secondmagnetic layer, respectively.
 15. The magnetoresistive element accordingto claim 9, wherein the first magnetic layer and the second magneticlayer are formed of a hard magnetic layer containing Co or Fe.
 16. Themagnetoresistive element according to claim 9, wherein the firstmagnetic layer and the second magnetic layer are disposed on the samesurface of the non-magnetic conductive layer with a distance whichdefines a track width of the magnetoresistive element.
 17. A magnetichead assembly comprising a magnetoresistive element comprising: a firstmagnetic layer and a second magnetic layer separate from each other, thefirst magnetic layer and the second magnetic layer each having amagnetization whose direction is substantially pinned; and anon-magnetic conductive layer electrically connecting the first andsecond magnetic layers, the non-magnetic conductive layer forming a pathof spin-polarized electrons from the first magnetic layer to the secondmagnetic layer, and the non-magnetic conductive layer comprising aportion located between the first magnetic layer and the second magneticlayer, the portion being a sensing area, wherein the non-magneticconductive layer is formed on an insulating layer so as to be in contactwith the first magnetic layer and second magnetic layer, the sensingarea of the non-magnetic conductive layer located between the firstmagnetic layer and the second magnetic layer has a length of 100 nm orless, and the magnetoresistive element has no magnetic layer in contactwith the sensing area of the non-magnetic conductive layer.
 18. Amagnetic head assembly comprising a magnetoresistive element comprising:a first magnetic layer and a second magnetic layer separate from eachother, the first magnetic layer and the second magnetic layer eachhaving a magnetization whose direction is substantially pinned; and anon-magnetic conductive layer electrically connecting the first andsecond magnetic layers, the non-magnetic conductive layer forming a pathof spin-polarized electrons from the first magnetic layer to the secondmagnetic layer, and the non-magnetic conductive layer comprising aportion located between the first magnetic layer and the second magneticlayer, the portion being a sensing area, wherein the non-magneticconductive layer is formed on an insulating layer so as to be in contactwith the first magnetic layer and second magnetic layer, the sensingarea of the non-magnetic conductive layer located between the firstmagnetic layer and the second magnetic layer has a length of 100 nm orless, and the magnetization of the first and second magnetic layers ispinned upward from an air-bearing surface.
 19. A magnetic reproducingapparatus comprising: a magnetic recording medium; and a magnetic headassembly comprising a magnetoresistive element comprising: a firstmagnetic layer and a second magnetic layer separate from each other, thefirst magnetic layer and the second magnetic layer each having amagnetization whose direction is substantially pinned; and anon-magnetic conductive layer electrically connecting the first andsecond magnetic layers, the non-magnetic conductive layer forming a pathof spin-polarized electrons from the first magnetic layer to the secondmagnetic layer, and the non-magnetic conductive layer comprising aportion located between the first magnetic layer and the second magneticlayer, the portion being a sensing area, wherein the non-magneticconductive layer is formed on an insulating layer so as to be in contactwith the first magnetic layer and second magnetic layer, the sensingarea of the non-magnetic conductive layer located between the firstmagnetic layer and the second magnetic layer has a length of 100 nm orless, and the magnetoresistive element has no magnetic layer in contactwith the sensing area of the non-magnetic conductive layer.
 20. Amagnetic reproducing apparatus comprising: a magnetic recording medium;and a magnetic head assembly comprising a magnetoresistive elementcomprising: a first magnetic layer and a second magnetic layer separatefrom each other, the first magnetic layer and the second magnetic layereach having a magnetization whose direction is substantially pinned; anda non-magnetic conductive layer electrically connecting the first andsecond magnetic layers, the non-magnetic conductive layer forming a pathof spin-polarized electrons from the first magnetic layer to the secondmagnetic layer, and the non-magnetic conductive layer comprising aportion located between the first magnetic layer and the second magneticlayer, the portion being a sensing area, wherein the non-magneticconductive layer is formed on an insulating layer so as to be in contactwith the first magnetic layer and second magnetic layer, the sensingarea of the non-magnetic conductive layer located between the firstmagnetic layer and the second magnetic layer has a length of 100 nm orless, and the magnetization of the first and second magnetic layers ispinned upward from an air-bearing surface.